 | |
 A signal bridge on the former Stony Brook Railroad in Graniteville | |
| Overview | |
|---|---|
| Current operator | CSX Transportation |
| Dates of operation | 1848–2022 |
| Technical | |
| Track gauge | 4 ft 8+1⁄2 in (1,435 mm) standard gauge |
| Length | 10.8 miles (17.4 km) 13.19 miles (21.23 km) (Originally) |
The Stony Brook Railroad (formally the Stony Brook Railroad Corporation), chartered in 1845, was a railroad company in Massachusetts, United States. The company constructed a rail line between the Nashua and Lowell Railroad's main line at the village of North Chelmsford and the town of Ayer, Massachusetts (then the village of South Groton) where it connected to the Fitchburg Railroad. Rather than running its own trains, upon opening in 1848 operations were contracted to the Nashua and Lowell; this arrangement continued until the Nashua and Lowell was leased by the Boston and Lowell Railroad in 1880. The Boston and Maine Railroad (B&M) took over operation of the Stony Brook in 1887 when it leased the Boston and Lowell Railroad. In 1983 the B&M was purchased by Guilford Rail System, which renamed itself Pan Am Railways (PAR) in 2006. Passenger service last ran on the line in 1961, but it saw significant freight service under Pan Am Railways. While it never owned rolling stock or ran trains, the Stony Brook Railroad Corporation existed until 2022 as a nearly wholly owned subsidiary of the Boston and Maine, itself a PAR subsidiary. That year, it was merged into CSX Transportation as part of CSX's purchase of Pan Am Railways.
The Stony Brook Railroad was named after Stony Brook, a tributary of the Merrimack River, which the line follows for several miles.